Process of treating water



Sept. 4, 19289 J. w. M. BOURGOGNION ETAL PROCESS OF TREATING WATER Filed May 17, 1927 2 Sheets-Sheet l Sept. 4, 19280 7 1,683,521 J. W. M. BOURGOGNION E1" AL PROCESS OF TREATING WATER Filed May 17, 192? 2 Sheets-Sheet 2 Clllrawurt lmnmvess 2 0 4 6 0 8 0 1 0 2 0 4.0 6.0 80 2 23 4 Patented Sept. 4, 1928.- I

UNITED STATES 1,683,521 PATENT OFFICE.

J'ULIANUS-WILHELM MEUSER BOURGOGNION AND CARL LUDWIG PHILIPS, OF

' NIJ'MEGEN, NETHERLANDS.

PROCESS OF TREATING WATER.

Application filed May 17, 1927, Serial Na-191,928, and in the Netherlands my 10, i926.

Our invention relates to a process for the treatment of water for houshold and industrial purposes. f

' It is a well known fact that soft .water i. e.

5 water containing only small quantities of Ca-, and (or) Mg-salts has an injurious effect upon metals and other substances such as concrete. With hard water this drawback also prevails though to a much smaller extent.

Although thisphenomenon cannot be aseribed to one single cause it has been found that'the so-called aggressive 00 plays a prominentpart in these cases.

In view of this fact it has heretofore been proposed to convert the CO for example into the form of Nal-ICO or Call-1C0 or, when dealing with naturally hard water, to remove the ()0 gas in order to eliminate 2 the corrosive effect. In these cases the nitrates and chlorides and also the oxygen which. are present remain in the water an the corrosive effect could not be completely eliminated in this way. i

The invention is based on quite a difierent' principle viz, on the well known phenomenon, that the Oaand (or) Mg-salt in sut? ficiently hard water will forma more or less coherent layer on the Walls of any vessel.

In the appendedclaims, the expression a hardening agent of the group including lime and calcium carbonate and the corresponding compounds .is intended to cover lime, calcium carbonate, magnesia or magnesiumcarbonate, any of which materials will dissolve in watercontaining 00 to give water'having a temporary hardness.

It has been found, that thislayer quite sufiices to protect the walls against any deleterious efi'ect.'

Fig. 1 represents part'of the curve showing the relation between the corresponding and fixed C0,; Fig.- 2 represents the relative values of the dissolving power ofwater as laid down by Miindlein. I

The process accordin to the invention includes,- especially, the increasingvthe temporary hardness of water which as a rule. is soft for household and industrial purposes,- inv order to artificially establishthe conditions necessary for the formation of" the said layer. 1

It has further been found, that there is one dominating factor which governs the result to be obtained when increasing the tempoequilibrium prevails, that is to say a certain solution.

-raryhardness for the said purpose as will be more fully explained'hereinafter.

The equilibrium of the "Ca-salts, which cause the temporary hardness of water may be represented by the following equation:

One half of, the co, which exists 'inthe ;form of the bi-carbonate is called: fixed ,CO the remainder of the CO which is present in the water is called: free CO and when the temperature and pressure are constant there exists a definite relation between fixed CO and free 00 when quantity of fixed CO corresponds to a definite quantity of free CO when the system is in equilibrium which quantity is called corresponding CO If the concentration of free CO in the 70 water is increased above the amount equal d to the corresponding (10,, the remainder of the free- 00 acts as aggressive CO Tlllmans and Heublein have determined in a number of cases the corresponding (10 with varying quantities of fixed CO the results have been laid down in a table; Fig.

1 represents part of the curve showing the relation between corresponding and fixed C0 The abscissae represent the fixed CO e. half of the CO ofthe bi-carbonate) whilst the ordinates show the free CO which, on the curve, is equal to the corresponding C0 The partof the drawing above the curve represents bi-carbonate solutions with an excess of CO the remainder represents solutions with a quantity of (30 which is insufiicient for theexistence of bicarbonate i. e. carbonate-solutions.

- Applicants have found that increasing the hardness of water will only yield the desired result, when precautions are taken, that the quantity of CO present equals the corresponding CO With more CO present the *excess acts as aggressive-CO with 'less 1 the system consists of aqueous carbonate.

Sov for example if water-is available of a hardness 9 (expressed in terms of fixed CO which is insufficient to form the desired precipitate on the walls of tubes or containers through which it is being conducted, and if the free CO contained therein is equal to the corresponding 00 (which is about 0) according to the invention CO 51h) free CO is about 1 (GD).

is led into the water until the amount of free CO is sufiiciently increased for example to 252.- In other words the original Water would be represented at A, in Fig.

1, and after absorption of CO led in, it

desired condition is reached in which, in

comparison with the untreated material, an increased hardness of 30 is obtained whilst the free CO is automatically reduced to the required amount of corresponding CO (about 1). The total amount of CO viz 31 does, of course, not undergo any change.

When carrying the process according to the invention into effect the diagram as shown in Fig. 1 will render valuable services as this diagram enables one toimmediately' determlne. the various values of CO re-.

quired. In the above instance the relation between free and fixed CO of the raw water is'represented by A. -After increasing the amount of CO by 22 the point B is reached and upon then treating the water with CaCO. or CaCO -containing substances'the relation between free and fixed C0 moves along the straight line BC which is at angle of 45 with the coordinates (along this line the total amount of CO remains con stant); point C represents the relation between free and fixed CO in the finished prodnot; the new hardness is equal to 30 in this water (point D) whereas the quantity of Should water of a temporary hardness 51 (point F) be desired, the preliminary treatment with CO should be continued until po1nt E is reachedas follows immediately from the diagram when projecting a straight line at an angle of 45 with the coordinates upward from F which meets the line AB at E at which point the temporary hardness 1s equal to 9 and the free CO is 45.

When conducting this water through a marble-filter (i. e. a casing containing chips of marble) a product with temporary hardness 51 is yielded'and with a quantity of free CO which in its turn is equal to the corresponding CO viz 3.

In Fire and Water Engineering 1925,

page 378 a process has been described in which the aggressive CO is taken up by treatment with lime (Ca(OH),); it is obvious, that in this case some CaCQ, may

form which will deposit on the walls oftubes or containers; itshould be noted however, that there is no certainty about ".the tem- 'porary hardness being sufliciently increased water may form a more coherent layer on the walls of tubes and containers than the original water would; it is obvious, that the water need only be treated in the said manner until the layeris .sufiiciently thick to withstand the action of usually soft water.

When increasing the temporary hardness in the described manner theamount of CO should not be raised above certain limits which are dependent on the material to be protected; a certain temporaryfhardness corresponds to a definite concentration of CO and this concentration governs in its turn the acidity of the water. Nowitis shown by Miindlein,-that the acidity (i. e. the H-ion concentration) is decisive for the dissolving power of water withvregard to various materials. Expressed in Tillmanss units (i. e. in 0.0001 111. g. H-ion) the dissolving power of alkaline water with h=1-.0 (which means that the water is neutral) is very large with respect to iron. The temporary hardness of water, which is to be conducted through iron pipelines or containers, should therefore not be increased above an acidity of h=025 which should be brought into account when preliminarily leading in CO (if necessary).

The values relative to 'the dissolving power of water have been laid down by Miindlein in a series of urves partly shown in Fig. 2.

The'above holds also good if Mg is present as a component. of the temporary hardness.

When the water, having the temporary hardness and havingthe proper relation between the fixed CO and free 00,, as above indicated, is passed through a pipe or vessel, the layer or coating of CaCO is formed automatically thereupon.

' Example.

Water of total hardness 2.1 D", a temporary hardness 2 D free CO contents of 9.96 m. g. per liter and free 0 of 4.8 i

m. g. per liter is very corrosive to metals for example to lead Pb) and iron (Fe). and will also dissolve aCO from concrete. If this Water is converted into water with temporary hardness 7 D-its free (10,-- contents being equal to the corresponding CO then this water will not any longer be injurious to concrete and only very little injurious to iron.

7 D temporary fixed C0 The corresponding quantity of CO can easily be determined from Fig. 1 as being 3.9; the total amount of CO is therefore 58.9 m. g.

Fixed CO is .present to the amount of 23 x 22 15.7 m. g, V and free CO tothe amount of 9.96 m. g. in total 25.7 m. g.

To this water should be added therefore CO per liter, after which it is conducted through a marble-filter.

I In case it should be desired to effect the neutralization of CO with the aid of lime,

hardness corresponds to it should be noted, that the combining of H 00 with Ca(OH) to bi-carbonate proceeds as follows:

For each 44 m. g. CO per liter the hardness increases by 5.6 D". If an increase of 5 D temporary hardness be desired,

CO =78.6 m. g. CO, (total) would be necessary. The corresponding CO of the new. hardness (7 D") is 3.9 m. g; 9.96 m. g. free CO being present 786- (9.963.9) =72.6 m. g. CO 'should be added.

Reference has been made above mainly to calcium compounds as the hardening agents, ture but obviously magnesium and the other alkaline earth metal compounds can be like- Ways,

wise included and are included in the scope of the invention wherever calcium is used in the claims. I

Rsum.0ur process, in its preferred form, will be seen to embrace three steps or conditions, in the following order- First. Having sufiicient dissolved CO in the water under treatment. (0)) Some waters may already contain a sufficient amount of CO for the purpose, and (7)) otherwise CO as such, will be added to and absorbed in the water, to bring up the free CO in the water to the required degree.

Second. The Water containing the required amount of CO then has its temporary hardness increased. (a) This can be done by treatment with CaCO, or MgCO (as by passing the water through a-marble filter, or otherwise) in which case any excess of the carbonate is in no way injurious, or (b) lime, in the required amount, can be added to the water.

Third. The water, thereby having had its temporary hardness increased to the desired extent and having the above stated ratio between fixed CO and free CO and free from aggressive CO may then be passed intothe pipe, tank or other device to be protected, under conditions suitable for the production of a coating of CaOO in said device.

What we claim is:' e

1. The process 'of treating water, which comprises increasing the temporary hardness thereof by treatment with a hardening agent selected from the group including lime and calcium carbonate, and the corresponding magnesium compounds, taking care althat the quantity of free CO present in the finished product is equal to the corresponding CO of the new hardness.

2. The process of treating water according to claim 1, which includes the step of increasing the quantity of CO in the water before treating the water with the calcium compound.

In testimony whereof we afiix our signa- .lULlANUS WILHELM MEUSER BOURGOGNION. CARL LUDWIG PHILIPS. 

